Drying and Cooling Stored Grain and Preserving its Quality

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1 Drying and Cooling Stored Grain and Preserving its Quality July 25, 2012 Dr. Greg Brenneman ISU Ag Engineering Specialist

2 Conditions that Lead to Storage Problems Grain that is too wet Grain that is too warm Trying to hold grain too wet, too warm, too long Fines accumulations Uneven grain temperatures in storage Grain not checked often enough

3 2012 Concerns - Aflatoxin A. flavus grows best in hot, dry years and warm nights. Storage conditions for A. flavus are degrees, 18% mc and damaged corn. Aflatoxin never goes down in storage remains the same or increases. Check fields prior to harvest if suspected.

4 Scout for Aspergillus Scout at BL and prior to harvest. Sample moldy corn to check aflatoxin levels. Dry moldy corn to less than 15% immediately. Google aflatoxin in corn

5 Grain temp Corn MAX Allowable Storage Time - Days Corn Moisture Content degrees F * * * * * * - Allowable storage is greater than 300 days

6 Soybeans MAX Allowable Grain temp Storage Time - Days Soybean Moisture Content degrees F * * * * * * * * * - Allowable storage is greater than 300 days

7 Corn Equilibrium Moisture Levels Temp 0 F Relative Humidity

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9 Tem p 0 F Soybean Equilibrium Moisture Levels Relative Humidity

10 EMC (%) Safe Grain Moisture Content (ERH = 65%) F 60 F 70 F 80 F 15 Winter Storage Summer Storage Corn Soybeans Temperature (C) Source: Purdue Univ.

11 Energy Efficiency Tips Use maximum drying temperature that does not damage the corn Energy requirements of a conventional high temperature cross-flow dryer as a function of drying air temperature and airflow rate. (University of Nebraska, about 1970) Airflow of Dryer Types Mixed Flow ~ 40 cfm/bu Cross-Flow ~ cfm/bu Airflow rate affects drying rate Vacuum Cooling

12 Drying Energy Cost Estimation High Temperature Drying~210 F Assumes 2,500 Btu/lb water Propane cost / bu- point moisture = x price/gal $ 0.033/bu-pt = x $1.50/gal propane, estimated propane cost to dry corn from 25% to 15% is $0.033/bu-pt x 10 pts = $0.33/bu.

13 Quantity of Propane Needed Propane gallons = x bu. x point moisture Propane = x 10,000 bu x 10 pts = 2200 gallons

14 Drying Time Natural Air 5-9 bu-pts / hour / hp Air 50 bu-pts / hour / hp Air 80 bu-pts / hour / hp Be careful with drying temps of 80 0 to corn can spoil faster than it dries

15 Fast Cooling Results in dry, cool grain that can go directly to market or into storage. Grain is still about 10 degrees F warmer than outdoor temperatures. Very little moisture loss during cooling. Subjects kernels to a lot of stresses that can result in cracking and breaking during handling.

16 In-Storage Cooling Hot grain is moved directly to storage and cooled slowly in the storage bin. Bin must be equipped with an aeration fan that is large enough to keep up with the dryer (need cfm per bu/hr of dryer capacity). Large fans can be cycled on and off. Grain will lose 1 to 1.5 percentage points of moisture during cooling.

17 Dryeration Grain is moved to a cooling bin and tempered (kept hot without cooling) for 4 to 12 hours. Grain is cooled (usually in less than a day) and then moved to storage. Grain loses about ¼ percentage point of moisture for every 10 degrees F of cooling (often 2+ percentage points). Reduces stress cracks.

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19 Grain Temp Differentials

20 Moisture Migration

21 Cooling Prevents Moisture Migration

22 How Long Does It Take to Cool Grain? Airflow rate is the key It takes about 15 cfm-hr/bu of fan operation Examples Drying fan 15 cfm-h/b 1.0 cfm/b = 15 hr Aeration fan 15 cfm-h/b 0.1 cfm/b = 150 hr Larger Bins Use electronic monitoring

23 Measuring Grain Temperature

24 Permanently Installed Grain Temperature Cables Cable Temperature sensor Temperature indicator Fan

25 Aeration Management Phase 1: Fall Cool Down Lower grain temperatures stepwise October November December F F F Phase 2: Winter Maintenance Maintain temperatures with intermittent aeration January, February F Phase 3: Spring Holding Keep cold grain cold Seal fans Ventilate headspace intermittently

26 Aerate Stored Grain (Spring) If grain isn t cooled below 30F, there might not be a need to warm it in the spring. If grain is cooled below 30F, it must be warmed in spring to prevent problems with condensation on the grain or frosting of equipment during summer. During grain warming, fans must be left on until warming is complete.

27 Aerate Stored Grain (Spring Grain must be dry. and Summer) Stored grain insects can be a problem, even in dry grain, if the temperature is too high. Avoid warming the grain above 50F. Avoid running aeration fans when the outdoor temp. is above 50F.

28 Cover Fans When Not Operating Prevents spring warm-up Keep snow & pests out Keep damp air out

29 Fines Management Fines are undesirable in stored grain because they increase airflow resistance and are easier for mold or insects to feed on. Clean grain before drying and storage. Or use a grain spreader to distribute fines throughout the grain mass. Or don t distribute fines and core bins to remove fines.

30 Checking Stored Grain Check every other week in winter. Check every week rest of year. Climb into the bin and feel for crusted, moist, sticky or warm grain. Probe the grain to with a thermometer checking for warm spots.

31 Correcting a Storage Problem Turn on the fan run until grain is cool Remove the problem grain Unload the entire bin

32 Work Safely Around Stored Grain! Use proper respiratory protection around dusty and/or moldy grain. Stay out of flowing grain. Watch out for bridged grain. Use fall protection when climbing bins or rail cars.

33 Keys to Successful Storage Store clean grain Dry grain to recommended moisture Aerate for a cool, uniform temperature Remove center cores of bins Check grain frequently Deal with any problems immediately

34 Where to go for more information Google post-harvest crops minnesota

35 Acknowledgments Managing Grain in Storage Bill Wilcke University of Minnesota Corn Storage and Drying Ken Hellevang North Dakota State University